Weird triangulation situation, not sure what to do now

Need some advice and don’t know who to go to, so I’m turning to the internet. Lol. My STBX (35M) and I (33F) had an ongoing huge disagreement lasting for basically the duration of our years-long marriage, which involves some deeply intimate personal details. We are calling it quits and there are a lot of reasons why, none of which are really what I’m writing about so I’ll leave that part out, but they all relate to this core issue in one way or another.

The specific thing I’m here for advice on is that throughout our marriage, there was a lot of triangulation going on that I didn’t clock for what it was until the very end. He would have these deep conversations with my family & friends about our disagreement, unbeknownst to me, and when we’d argue, he’d trot out the latest conversation he’d had with whomever. That list included Jessica (32F), my BFF since we were tiny, which will be relevant in a moment. He’d tell me that they were on his side, and everyone thought I was doing wrong by him. Which turned out to be untrue, but I didn’t find that out until my confidence in many/most of my relationships had already taken a big hit.

The last straw came when he and Jessica went off by themselves for several *hours* at a dinner party, actively avoided being overheard and both got the deer-in-headlights look when they saw me walk around a corner but basically ignored me and zoomed off to keep talking. It was super awkward for everyone. As far as I knew at that point, they were friendly but not close, so it was even more awkward. I know they were talking about me, because multiple people overheard them. He and I fought about it later and he said they were only talking about me for part of that time, and I wouldn’t be so upset if I’d heard what they were saying (but then why make such a production out of making sure I didn’t hear what they were saying…?). When I talked to her about it, she completely left out the fact that they’d talked about me at all, when I specifically asked why that interaction had been so weird.

I don’t think they were having an affair or whatever. Still, I would NEVER in a million years have the kind of conversation they were apparently having (the whole thing, not just the bits about me) with her husband. I get that everyone has different levels of comfort with intimacy in conversations, but this was just weird given who was involved. I also wouldn’t have that same conversation with my husband’s relatives, because (a) it’s too intimate and (b) I believe everyone deserves to have “their” people to confide in, and I’m not going to try to persuade someone else’s lifelong confidantes that they should see things my way and convince him to fall in line. The issue with him is a moot point at this stage, but I’m still left with what to do about my relationship with her.

I’ve since learned that at least one family member told her before this went down to stay out of the issues in my marriage, so apparently this was a whole thing and I just didn’t know about it. She obviously didn’t take that advice, and still doesn’t see anything wrong with that. She’s said that she’s sorry I’m upset and that it seems like I have a shaky belief in our relationship (um, I didn’t before but I do now, that’s why I’m upset?). Not sorry for the huge breach of boundaries, not sorry for the effect on me. I don’t blame her entirely for ending up in the situation, and my marriage ending was not about her at the end of the day, but I’m still deeply upset. It’s been several weeks now and I’m still shocked more than anything because she was my ride or die and now I feel like I don’t even know her. I don’t know how to feel now or what to say next time I see or talk to her. But I’m going to see her at another party in a month or two. Should I call her back again when I’ve had a few more days to cool down? What would I even say?

TL;DR my marriage ended recently, and the catalyst was a triangulation situation with my BFF. Not sure how to patch things up with her or if I even really want to.